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Discussion Starter · #21 ·
A photo? I could take one. It definitely isn't real micranthemoides, but what species exactly is proving to very difficult to pin down. Not knowing where it came from originally makes it doubly so. Might be undescribed.
 

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Discussion Starter · #23 ·
I wonder if the "Toro *****" one from Puerto Rico:
http://www.aquaticplantcentral.com/forumapc/plant-id/72895-need-id-plants.html
http://amepr.createforumhosting.com/planta-del-rio-t6645.html
and Neil's and Paul's 2-leaf Hemianthus are the same plant.
I think they might be.

In the Micranthemum indet file (species uncertain), I found about seven specimens of a plant that really, really looks like the '2-leaf'. Leaves are opposite. All were from the Dominican Republic and look like what we'd call Hemianthus if the two genera are kept separate (and I suspect they should be). It could very well be the same as the plant from PR. Oddly, the flora I found gives only Hemianthus callictrichoides and Micranthemum umbrosum as occurring in the DR. This is evidently neither of them. Some very old labels on them had them as Callitriche , but that's obviously not the case, and a newer annotation refuted that but stopped short of putting a better name on it (there's some really strange stuff on old specimens from the days before our more advanced understanding of plant relationships). Neither I or anyone else has had a thorough look at it, but I'll give an update if that happens. At least, this may be progress. A real mystery!
 

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Discussion Starter · #25 ·
It was a bright green carpet in ditches and wet depressions. Even puddles in dirt roads. It was pretty dry when we went, but those areas are under water much of the year.
 

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Some very old labels on them had them as Callitriche
When I first got the 2-leaf Hemianthus, it reminded me of a Callitriche :)

The question of what the current genus is for these species appears to be unresolved. They are sometimes included in Micranthemum. For now, I propose we continue to include them in Hemianthus.
In Cook 1996, Aquatic Plant Book, Micranthemum and Hemianthus are distinguished by present vs. absent (or rudimentary) upper lip of corolla. If this difference is consistently present, and if each genus is monophyletic (a natural group), surely there is nothing to be said against distinction between Micranthemum and Hemianthus.
 
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